Fiber optic cables are used to transmit light in fiber-optic communications and optical sensing. For example, in optical sensing, light can represent various signal types, such as temperature, pressure, strain, acceleration, and the like. In some applications, optical sensing can be used in a wellbore by communicating light between a source and downhole sensors or actuators (or both). The fiber optic cables can be embedded in the wellbore's casing, or run down into the wellbore with a well tool (e.g., a logging tool string in a drill pipe string). As light passes through a fiber optic cable, some photons are lost to natural fiber attenuation through imperfections, impurities, and natural scattering processes. The rate at which photons are lost depends on factors including wavelength, hydrogen ingression and bending loss. Loss of photons affects a wavelength of light available downhole for sensing applications.
Like reference numbers and designations in the various drawings indicate like elements.